Can't download HD movies from iTunes......why?

Can someone please tell me why I can't download any HD movies from iTunes anymore? The link is greyed out and it says "The HD version of this movie is available on Mac or Windows 7 computers with HDCP components".

I can understand not being able to watch the movie unless I have HDCP components, but I should at least be able to buy it on another computer (work for example), and then transfer it to my library at home.